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Feb. 14. 1956 J. E. JONSSON METHOD OF PRODUCING CONTACT SPRING SETS 2 Sheets-Sheet 1 Filed April 24. 1951 :2 22,0 emf/Ol E. Jonas 012,

Feb. 14. 1956 J. E. JONSSON METHOD OF PRODUCING CONTACT SPRING SETS 2 Sheets-Sheet Filed April 24. 1951 oo o Fig. 4-

United States Patent METHOD OF PRODUCING CONTACT SPRING SETS Johan Edvin Jonsson, Hagersten, Sweden, assignor to Telefonaktiebolaget L M Ericsson, Stockholm, Sweden, a company of Sweden Application April 24, 1951, Serial No. 222,541 7 Claims priority, application Sweden May 5, 1950 3 Claims. (Cl. 29-15555) The present invention relates to a method for production of contact springs for contact spring sets in electromagnetic connecting devices. When contact springs are put together to a group in a connecting device, insulating intermediate layers are usually placed between the supported parts of the springs or else grooves made in an insulating fastening device, in which the springs are inserted. These assembly methods are, however, very troublesome and time-consuming. It has also been proposed to mould a set of contact springs at one time into an insulating block but great difficulties have arisen in avoiding deformation of the single springs at the penetration of the moulding compound and due to this erroneous voltages in the free parts of the springs. This invention has for a purpose to avoid these inconveniences with simple means. This is achieved in such a way that the contact springs before the assembly are moulded individually with an insulating envelope, so that the springs thereafter may be piled directly on each other and fixed to the apparatus by means of fastening devices. So as not to have a spring in any way actuated by the moulding compound during the operation the part intended for supporting is controlled by especial guide pins in the moulding tool during this operation.

The invention will be described more closely in connection with the enclosed drawings. Fig. 1 shows a contact spring without an insulating envelope. Fig. 2 shows three such contact springs with moulded, individual insulating envelopes 10 and ready for assembly in a connecting device.

The contact spring shown in Fig. 1 has a resilient part 11 with contact points 12, a part 13 intended for fastening or supporting and finally a smaller part 14 comprising a soldering peg for connection of connecting wires. According to the present invention such contact springs are inserted individually in a moulding tool for thermoplastic substances. The part 13 intended for fastening is placed in the moulding cavity and the adjoining parts 11 and 14 control the spring of the tool. In the latter there are three pegs for forming partly two holes 25 for fastening the contact springs together to a contact group and partly a steering hole 26. In the contact spring, Fig. 1 there are corresponding holes 15, 16 in the part intended for fastening. The two remotest parts of these have, however, a somewhat greater diameter than the pegs of the moulding tool. When the thermoplastic substance is pressed into the tool these holes are therefore partly filled with plastic substance, so that no electric connection can arise between the difierent springs, when these are fixed together by means of screws 23 or the like. In the moulding tool four small pins are placed on each side of the moulding tool, which pins hold the part intended for fastening in a fixed position in order to prevent this part item being bent, when the moulding compound penetrates into the tool. In the insulating envelope 10, which after the moulding surrounds the contact spring, four small holes 24 are formed behind these guide pins on each side of the contact spring. In Fig. 2 we see the holes 24 2,734,257 Patented Feb. 14, 1956 on the upper side of the insulating envelope. The corresponding holes are also to be found on the under-side, but these are so placed, that they are not lying straight in front of the holes on the upper side, as in such a case points would arise on the spring, which lack insulation. The moulding tool is further so shaped that the moulded insulating envelope is shaped with protuberances 27 on one side and recesses 28 on the other side, so adjusted in relation to each other, that the protuberances fit into the recesses, when the springs are piled on each other. Uppermost in Fig. 2 two such springs are laid on each other and ready to be fixed on a relay or another connecting device by means of screws 23 fitting into the holes 25.

At the proposed moulding operation it has proved suitable to use plastics of polystyrol type as insulating compound, said plastics being of such a quality that it has a high stability of form when heated. The insulating envelope obtained at the moulding needs not be worked in any especial working operation, after the contact spring has been taken out of the moulding tool, but the spring can be assembled directly in the apparatus. If one wishes that the spring shall possess a certain voltage at the assembly this can be obtained in such a way that the guide pins of the moulding cavity are so arranged that the single contact spring at the insertion in the tool is bent, whereafter the insulating compound is moulded around.

The proposed method is especially adapted for contact springs cut out of plate bands, which springs are put together in one or more contact groups. In Figs. 3 and 4, which show difierent views of a material band with contact springs partly cut out, it is supposed that a material band 111i, in a known manner has been fed past a machine not shown, which punches spaces 111, 112 between the contact spring blanks 113, so that these only partly are united by plates 114, which are not punched out. The three shown contact blanks 113 are thereafter placed together in a moulding tool and moulded simultaneously each by itself with the insulating envelopes 115 along the part of the springs intended for fastening. After the moulding operation the springs are cut off from each other due to the fact that the plates 114, which are not punched out, are cut away. At the same time the funnel 16 arisen at the moulding operation is removed.

More than three contact spring blanks may of course be inserted simultaneously in the moulding tool and provided with individual insulating envelopes. Insulated springs in cakes or bands are thereby obtained. After the plates 114 and the funnel 116 have been removed these contact springs are connected by a thin layer of moulding compound between the insulating envelopes 115, said layer generally arising at the moulding operation. At the moulding one can of course also arrange beams of mouldmg compound, which keep the springs together.

The contact spring sets are then assembled by these connected spring bands and after the assembly the rests of the moulding compound, which exist between the insulatmg envelopes, are removed. As to such contact groups at which two or more contact springs are assembled beside each other, it may be advantageous to punch out the spring blanks with that space, which they shall have in the group.

In a similar manner as single contact springs are piled on each other and joined together a number of connected contact springs may of course be piled on each other simultaneously and fastened together to a large group. Said fastening of the insulating envelopes may take place through an especial method. This takes place in such a way that after assembly and squeezing together of said spring bands provided with individual insulation a pencilling or spraying of the insulating envelopes takes place by means of benzol or some other dissolvent. The benzol penetrates thereby capillarily and joins the group. together. The moulding compound remaining between the insulating envelopes is then removed. The insulating envelopes may of course also be united by means of some suitable pasting-means, which is applicated on the surfaces-of the insulating envelopes lying against each other, before they are pressed together.

I claim:

1. The method of making fiat contact springs for relay pile-ups and the like, and of the type having a flexible contact end, a terminal connector end and an intermediate portion for mounting of the spring in a pile-up, said method being characterized by control of the spring tension in the intermediate portion, comprising: providing a contact spring of flat sheet metal having at least one aperture in its intermediate portion, supporting said spring with its intermediate portion in a moulding die recessed about the intermediate portion, contacting spaced points on opposite faces of the intermediate portion by fixed guide pins to define the plane occupied by the said intermediate portion, the guide pins contacting dilferent areas of the intermediate portion on its opposite faces, moulding insulation material in said die entirely about said intermediate portion including the wall surface of said aperture, and about said guide pins, and removing said contact spring from said die after said insulation material has hardened.

2. The method in accordance with claim 1, including the stepof moulding. complementary locatingformations on the opposite surfaces of. the insulation material surrounding said intermediate portion of the spring, and assembling a group of the finished springs in face-to-face contact with their said locating formations in alignment with one another, and with the holes produced by said guide pins out of alignment as between any two mating faces of adjoining springs.

3. The method in accordance with claim 2, including the step of securing the springs of said group to one another in face-to-face contact by adhering to one another the contacting faces of the insulation of respective adjoining springs.

References Cited in the file of this patent UNITED STATES PATENTS 1,689,340 Hearn Oct. 30, 1928 1,921,430 Reynolds Aug. 8, 1933 2,254,720 Wilcox Sept. 2, 1941 2,339,434 Stehlik Jan. 18, 1944 2,350,887 Golf June 6, 1944 2,373,861 Van Inwagen Apr. 17, 1945 2,458,552 Blattner Jan. 11, 1949 2,483,024 Roters Sept. 27, 1949 2,670,530 Regnier Mar. 2, 1954 FOREIGN PATENTS 201,092 Great Britain July 26, 1923 

